It is known to use laser beams to process objects, for example to change material properties of an object, or to remove material from an object. For this purpose a laser beam having a sufficiently high beam energy and adequate photon energy is directed via a laser scanner at previously determined processing locations of the object. This is achieved by setting scan deflections of the laser scanner as a function of coordinates of the processing locations in a coordinate system of the laser scanner. For this purpose, the coordinates of the desired processing locations are converted into deflections of the laser scanner. This can be achieved by a suitable mathematical coordinate transformation.
Such coordinate transformation is preferably calibrated. This can be achieved, for example, by using of a detector, arranged behind an aperture which has a known diameter and is arranged at a known location in the coordinate system, by the laser beam being scanned by the laser scanner through the aperture. The laser beam scanned through the aperture can be the laser beam with which the processing of the object is also carried out, or it may be a different laser beam, the beam path of which has a known relation to the laser beam with which the processing of the object is carried out. In accordance with signals detected by the detector, the scan deflection of the laser scanner corresponding to the location of the aperture can be determined, and the coordinate transformation thereby calibrated. This process can be repeated for a plurality of known locations at which the aperture is arranged. Such devices and methods are known from U.S. Pat. No. 6,501,061 B1 and US 2005/0205778 A1, the full disclosure of which is incorporated into the present application by reference.
Determining the position of the aperture relative to the laser scanner based on the signals detected by the detector involves a significant period of time, which extends the overall processing time for an object with a laser processing system.